What is the ruling of Islamic law if a person is uncertain whether he has divorced his wife or not?

Islam gives the husband the right to divorce his wife and the final say whether or not to put it into effect. Therefore, if a husband is uncertain whether he has divorced his wife or not, he has not divorced her as the marriage bond is confirmed with certainty. Therefore, the marriage remains valid unless there is certainty or an overwhelming conjecture that it is not. This is expressed by the juristic axiom, 'Certainty is not removed by doubt'.

If the husband has doubts about having divorced his wife or if he makes the divorce conditional on something which he is not certain that she has abided by like when he tells her, ‘If you do not do such-and-such, you are divorced,” and he is not certain whether or not she has obeyed him, she is not divorced. If the uncertainty is on the wife’s part, divorce does not take place as the husband has the final say in this regard.

Al-Khatib Al-Shirbini (may God bless his soul) said: “If the husband doubts whether he has divorced his wife or not or that she did not abide by his condition like, ‘If that bird is a raven, you are divorced,’ but is uncertain whether or not the bird is a raven, we do not rule that divorce has been effected.” Al-Muhamaly said in Mughni Al-Muhtaj (4/491): “This verdict is based on the consensus of Muslim scholars because the religious principle in this case is, divorce has not been effected and that the marriage bond continues to be valid.”

The couple in question should fear God the Almighty, and the wife should not deny her husband`s right to sex with her unless she is absolutely sure that divorce has indeed been effected.
And God the Almighty knows best.